Fundamental behavioral processes such as associative learning, rate calculation and decision making crucially rely on estimation and reproduction of time intervals in the seconds-to-minutes range (interval timing). One of the underlying assumptions of most timing theories is that subjects are able to readily abstract from the input stimulus the temporal information, and to tune their behavior according to this cue, irrespective of non-temporal properties the real timed event. In contrast, evidence suggests that both animal and human timing is highly sensitive to properties of the timed signal thus supporting the notion of an "attentional switch/gate" interval timing mechanism. The objective of this proposal is to study attentional processing of temporal information in the seconds-to-minutes range (interval timing) using a multi-level, behavioral, neuropharmacological, and computational approach. Behaviorally, the investigator will study a newly developed interval timing procedure shown to engage attentional processing of temporal cues. Within this procedure, the investigator proposes to evaluate the impact of the characteristics of stimuli on timing and memory for timing. Pharmacologically, the investigator proposes to dissociate the clock effects and attentional effects of specific dopamine agonists and antagonists on interval timing. We also propose to investigate the neural substrates involved in the attentional switch/gate mechanism of timing. Computationally, the investigator proposes to develop a model of the attentional switch/gate mechanism of interval timing in order to address the effect of behavioral and pharmacological manipulations on attentional processing of temporal information. The studies will inform current models of timing, time perception, and neuropharmacology of interval timing. They will provide new means for understanding the impact of attentional factors on complex cognitive mechanisms that require temporal processing. They will help elucidate the pharmacological and neural basis of attentional processing of temporal information